Optimizing conditions for the extraction of catechins from green tea using hot water.

Six different factors involved in the extraction of catechins from green tea using water were examined for their impact on the yield of catechins and on the efficiency of water use. The best temperature and time combination for catechin extraction was at 80°C for 30 min. The yield of catechins was also optimal with a tea particle size of 1 mm, a brewing solution pH <6 and a tea-to-water ratio at 50:1 (mL/g). In terms of efficient use of water in a single extraction, a water-to-tea ratio of 20:1 (mL/g) gave the best results; 2.5 times less water was used per gram of green tea. At the water-to-tea ratio of 20:1 mL/g, the highest yield of catechins per gram of green tea was achieved by extracting the same sample of green tea twice. However, for the most efficient use of water, the best extraction was found to be once at a water-to-tea ratio of 12:1 (mL/g) and once at a water-to-tea ratio of 8:1 (mL/g). Therefore, all six of the factors investigated had an impact on the yield of catechins extracted from green tea using water and two had an impact on the efficiency of water use.